Compounds having this basic structure and a dialkylaminoalkoxy radical in para position to one of the phenyl radicals on the C-atom 1 of the but-1-ene chain are already described in British Patent Specification No. 1,013,907. One of them, the (Z)-1-[4'-(2-dimethylaminoethoxy)phenyl]-1,2-diphenylbut -1-ene (tamoxifen, INN rec.) is a specific estrogen antagonist. By virture of its marked anti-estrogenic activity, this active ingredient has already proved successful in the therapy of hormone-dependent mammary.
German Offengsschrift No. 2 807 599 has discliosed that a metabolite of tamoxifen, the (Z)-1-[4'-(2-dimethylaminoethoxy)phenyl]-1-(4'-(2-hydroxyphenyl)-2-phenylb ut-1-ene ("4-hydroxytamoxifen") has an antiestrogenic effect comparable to tamoxifen. As reflected by European application No. 0 002 097, this also applies to a series of 1-[4'-(2-alkylaminoalkoxy)phenyl]-1-(4'-hydroxyphenyl)-2-phenylbut-1-enes ("4-hydroxytamoxifen derivatives").